1. Field of the Invention
The present invention relates to a vehicular illumination lamp that utilizes a light emitting device as a light source.
2. Related Art
In recent years, vehicular illumination lamps, which utilize light emitting devices such as light emitting diodes as light sources, have been proposed for adoption as headlamps or the like.
For example, Japanese Patent Publication No. 2003-317513 (“JP '513”) describes a so-called projector type vehicular illumination lamp, which includes a projection lens disposed on an optical axis which extends in a longitudinal direction of the lamp and a light source unit disposed rearwards of the projection lens. The light source unit of the vehicular illumination lamp described in JP '513 is configured so as to include a light emitting device disposed near the optical axis at a position situated further rearwards than a rear focal point of the projection lens, and a reflector disposed in such a manner as to cover the light emitting device from thereabove so as to reflect light from the light emitting device towards a front of the lamp while causing the light to get closer to the optical axis. Then, a light distribution pattern is formed as an inversely projected image of a light source image that is formed on a rear focal plane of the projection lens, when the light source unit is turned on.
When adopting a lamp configuration such as that described in the aforesaid JP '513, it is possible to form a predetermined light distribution pattern while enhancing the utilization factor of a bundle of rays of light from a light emitting device.
In the vehicular illumination lamp described in the aforesaid JP '513, however, since the light source is made up of the single light emitting device, there is a limitation on the brightness of a light distribution pattern that is formed by light emitted from the light source, even if the utilization factor of a bundle of rays of light emitted from the light emitting device is enhanced to a maximum level. Consequently, in a case where this vehicular illumination lamp is used as a lamp unit for a headlamp, there is a problem that many such lamp units are necessary.
The invention was made in the light of these situations, and an object thereof is to provide an vehicular illumination lamp utilizing a light emitting device as a light source which can secure a sufficient brightness for a light distribution pattern that is formed by light emitted thereof.